1. Field of the Invention
The present invention relates to an encryption communication system and, more particularly, to an encryption communication device capable of improving the generation of a password and reducing the complexity of encryption.
2. Description of the Background Art
Various kinds of encryption systems have recently been put to practical use for the security of communication and data. The encryption systems include a DES (Data Encryption Standard) system and an RSA (Rivest, Shamir and Adleman) public key cryptosystem. The DES system is a public key cryptosystem of encryption algorithm publication type, i.e., the combination of positional shift and character replacement. The RSA public key cryptosystem is not feasible for the encryption of mass data because of the huge amount of calculations. The RSA system is often used for the certification and the sharing of a key between two parties prior to secret communication.
Today, the forgery of various cards including prepaid cards and telephone cards is a of social problems needing urgent remedy. Also, the problem with computer communication is that unauthorized persons often steal passwords with the intention of hacking into computers and a communication network. Although some degree of encryption is effected with existing computer systems and communication systems for the security purpose, not all the systems and terminals are provided with an advanced encryption scheme. Moreover, advanced encryption is not practicable without resorting to a sophisticated program and a sophisticated circuit arrangement. It is therefore difficult to effect advanced encryption with miniature data terminals and devices.
IC (Integrated Circuit) cards are now replacing magnetic cards due to large storage capacity available therewith. With IC cards, it is possible to totally manage various kinds of information necessary for daily life, e.g., financial information and private information. Further, there has been proposed to apply IC cards to telephone cards, prepaid cards for trains, and prepaid cards for pachinko and other games. Encryption is essential even with such IC cards in order to secure the above information and to protect the IC cards from eavesdroppers when connected to a host for communication. In addition, this encryption must be done with a miniature arrangement.
Some different encryption schemes are practiced with up-to-date computer communication systems for the communication and data security purpose, and each is implemented by a sophisticated combination of numerical values and sentences. However, even the numerical values and sentences combined in a sophisticated way might be decrypted by use of a large capacity, high speed computer if static (uniform and simple) numerical values and sentences were combined.